D/A CONVERTER

PURPOSE:To raise the resolution and to increase a response speed only by heightening the repeating period of a rectangular wave output by calculating a duty ratio from an input digital value, obtaining the rectangular wave output of the duty ratio, integrating this and obtaining an analog output. CONSTITUTION:A digital value fetched to a register 11 is supplied to a duty modulator 12 and the duty ratio is calculated from the digital value. A signal SC is outputted which comes to be a high level at an on time and a low level at an off time. The signal SC is supplied to a switch circuit 13, porality-inverted by an inverter 14 and supplied to a switch circuit 15. By a resistance 16 and a capacitor 17, the signal SC is integrated and smoothed and removed through an amplifier 18 as the analog output of an output edge 19. When the rectangular wave output from a duty modulator 12 is made into, for example, an on time and two clock period parts and three clock period parts are alternately outputted, the output of the accuracy of a 0.5 clock period can be obtained.